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Unformatted text preview: Name: ___________________________ 1 7.06 Cell Biology EXAM #3 November 21, 2006 This is an open book exam, and you are allowed access to books and notes but not computers or any other types of electronic devices including cell phones. Please write your answers in pen (not pencil) to the questions in the space allotted. Please write only on the FRONT SIDE of each sheet. And be sure to put your name on each page in case they become separated! Remember that we will Xerox all of the exams. Good luck! Question 1. 25 pts __________ Question 2. 25 pts __________ Question 3. 25 pts __________ Question 4. 25 pts __________ Name: ___________________________ 2 Question 1 (25 points) You have joined a lab that works on cell motility. One of the cell lines this lab studies is a keratinocyte line. Unsure as to how these cells crawl, you ask the graduate student in the lab a number of essen- tial questions. A. (1 point) What are the protrusions called at the leading edge of the crawling cell? B. (2 points) Propose an experiment to show that the movement of keratinocytes is mediated by the actin cytoskeleton. You do not need to describe extensive experimental detail. C. (4 points) How do you measure the critical concentration of G-actin necessary for actin Flament formation? Be sure to add experimental detail. Name: ___________________________ 3 D. (4 points) How would addition of a seed affect the kinetics of Flament formation? Armed with all the information necessary to get a start on your project you Frst decide to determine the critical concentration for the (+) end and the (-) end. E. (6 points) Describe an experiment that would allow you to determine the critical concentration for the two ends including experimental detail. F. (4 points) Having established the critical concentration for the (+) end as 0.6µM and that of the (-) for 1.6 µM, at what speciFc Cc would treadmilling – as deFned as actin Flament movement without net Flament length change (steady state) – occur? Explain your reasoning. G. (4 points) At which concentration would the net-Flament length increase? At which would net-Fla- ment length be lost? Name: ___________________________ 4 Question 2. (25 points) You are studying a new transcription factor, HFL1, that is phosphorylated following addition of TGF-ß to your line of cultured mouse lung epithelial (MLE) cells. TGF induces expression of the PAI1 gene in these cells and a colleague of yours has generated evidence that HFL1 protein, when phosphory- lated, binds to the PAI1 promoter and induces PAI gene expression. You do not have an antibody to HFL1. Your thesis advisor, Prof. Lodish, wants you to ¡nish an important set of experiments on this protein quickly so the lab can publish a paper on HFL1 in Cell; he does not want to wait until you have...
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